This invention relates to valves, and more specifically to an adjustable self-cleaning, vernier control needle valve.
Metering valves utilizing a needle and seat arrangement are commonly used for adjustably metering and controlling low flat rates of fluids. A problem normally encountered with the use of such valves is the tendency of the valve to accumulate debris and foreign matter in the area of restricted flow between the needle and orifice, resulting in fluctuations and inaccuracies in the flow of fluids through the valves. In the past, to clean the valve, it has been necessary either to reverse the flow of fluid through the valve or alter the adjustment to open the valve allowing the greater flow rate of the fluid to wash the debris out of the needle and orifice area. Such adjustment or reversal of fluid flow has been found to be difficult and impractical particularly in precision or needle-type metering valves, since it requires that the valve be reset to its original position after flushing which is time-consuming and subject to error and in the past no provision has been made in precision metering valves for a means to allow quick and easy opening of the needle and orifice area to allow the debris to be flushed through the valve and then returned to the former precise setting without requiring re-adjustment of the valve.